Patent classifications
E
FIXED CONSTRUCTIONS
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E21
EARTH OR ROCK DRILLING; MINING
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E21B
EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
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7/00
Special methods or apparatus for drilling
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E21B7/28
Enlarging drilled holes, e.g. by counterboring
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E21B7/30
without earth removal
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